Treatment of resistant or refractory cancers with multi-arm polymeric conjugates of 7-ethyl-10-hydroxycamptothecin

ABSTRACT

A method of treating a resistant or refractory cancer in a mammal includes administering an effective amount of a compound of 
     
       
         
         
             
             
         
       
     
     to the mammal. In preferred aspects, the cancer is resistant or refractory to CPT-11 or CPT therapy.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 12/028,378 filed Feb. 8, 2008, which claims the benefit ofpriority from U.S. Provisional Patent Application Ser. No. 60/900,592filed Feb. 9, 2007, the contents of each of which are incorporatedherein by reference.

FIELD OF INVENTION

The present invention relates to a method of treating resistant orrefractory cancers. In particular, the invention relates to a method oftreating cancers resistant or refractory to camptothecin or CPT-11 usingpolyethylene glycol conjugates of 7-ethyl-10-hydroxycamptothecin.

BACKGROUND OF INVENTION

Over the years, there have been reports that many common cancers haveshown resistance or refractory phenomenon to curative therapies. Somecancers do not respond or respond initially but shortly thereafter, theybecome resistant to the therapies. Other cancers fail to respond totherapies which include subsequent rounds of treatment after earliersuccessful rounds of treatment. In other cases, cancers recur severalyears after completing effective treatment. If the resistance orrefractory phenomenon to chemotherapy, radiation therapy or other cancertherapies could be prevented or overcome, it would be a great advance inmedicine.

Various anti-cancer agents have been developed in efforts to treatcancers. Many of those potential anti-cancer agents have unfortunatelyshown drug resistance through a variety of mechanisms. Some tumors donot respond to certain types of anti-cancer agents after initial shorttherapeutic responses are shown. In some cases, tumor shrinkage reversesand tumors start to grow again in spite of the cancer initiallyresponding to anti-cancer agents.

One potent anti-cancer agent is camptothecin. Camptothecin and relatedanalogs are known as DNA topoisomerase I inhibitors. Irinotecan (CPT-11,Camptosar®) is a currently marketed DNA topoisomerase I inhibitor withsome anticancer activity. Although not currently marketed, an activemetabolite of CPT-11, 7-ethyl-10-hydroxycamptothecin, is thought to alsohave some anticancer activity. Like other anticancer agents, drugresistance has been observed with the use of camptothecin andcamptothecin derivatives. For example, resistance to 9-amino or 9-nitrosubstituted camptothecins has been reported in common cancers. See U.S.Pat. No. 6,194,579.

Various proposals have been made to overcome drug resistance orrefractory phenomenon associated with anti-cancer agents. One earlyattempt to overcome the barrier associated with camptothecin orcamptothecin analogs was directed to developing less toxic CPTderivatives. Other attempts include uses of potential drug resistanceblockers such as an epidermal growth factor receptor antagonist andNa⁺/K⁺ ATPase inhibitors. See US Patent Publication Nos. 2002/0012663and 2006/0135468.

In spite of the attempts and advances, there continues to be a need toprovide a method of treating a resistant or refractory cancer. Thepresent invention addresses this need.

SUMMARY OF INVENTION

In order to overcome the above problems and improve the therapy fortreatment of cancers, there is provided a method of treating a resistantor refractory cancer in a mammal.

In one aspect of the invention, there is provided a method of treating aresistant or refractory cancer in a mammal, including:

administering an effective amount of a compound of formula (I):

wherein

R₁, R₂, R₃ and R₄ are independently OH or

-   -   wherein    -   L is a bifunctional linker;    -   m is 0 or a positive integer; and    -   n is a positive integer;    -   provided that R₁, R₂, R₃ and R₄ are not all OH;        or a pharmaceutically acceptable salt thereof to the mammal.

In one particular aspect of the invention, the polymeric prodrugs of7-ethyl-10-hydroxycamptothecin for treatment of the resistant orrefractory cancer employ four-arm PEG-7-ethyl-10-hydroxycamptothecinconjugates having the structure of

wherein n is from about 28 to about 341, preferably from about 114 toabout 227, and more preferably about 227.

The resistant or refractory cancers which can be treated with themethods described herein include solid tumors, lymphomas, lung cancer,small cell lung cancer, acute lymphocytic leukemia (ALL), breast cancer,colorectal cancer, pancreatic cancer, glioblastoma, ovarian cancer andgastric cancer. The forgoing list is not meant to be exclusive and thoseof ordinary skill will, of course, realize that other resistant orrefractory cancers not specifically mentioned herein are intended forinclusion.

One aspect of the invention provides the method of treating cancersresistant or refractory to chemotherapy. In one particular aspect, thetreatment is effective for cancers resistant or refractory tocamptothecin (CPT) or CPT-11 associated therapy. Alternatively, thepresent invention provides a method of treating cancers showingtopoisomerase I mediated resistance or refractory phenomenon.

In another aspect, the present invention provides a method of treatingcancers resistant or refractory to therapies associated withadministration of polymeric prodrug forms of CPT or CPT-11 such aspolyethylene glycol conjugates of CPT or CPT-11.

The polymeric prodrugs of 7-ethyl-10-hydroxycamptothecin according tothe present invention are effective to cancers resistant or refractoryat the onset of treatment or subsequent round therapies. The presentinvention allows treatment of refractory cancers that are sensitive toCPT-11, i.e. which appear to be inhibited in the first round treatmentbut become resistant to in the second or subsequent rounds of therapies.The polymeric prodrugs of 7-ethyl-10-hydroxycamptothecin can be furthereffective for treatment of recurring cancers after treatment isdiscontinued.

In another aspect of the invention, the polymeric prodrugs of7-ethyl-10-hydroxy-camptothecin are administered in amounts of fromabout 0.1 to about 45 mg/m²/dose based on the non-polymer portion of theconjugate. The polymeric prodrugs described herein are administered onceevery three weeks for each treatment cycle or once weekly for threeweeks, followed by one week rest period for each cycle until the desiredresults are observed.

One advantage of the present invention is that patients can be treatedconcurrently or sequentially with an effective amount of the polymericprodrugs of 7-ethyl-10-hydroxycamptothecin in combination with anotheranti-cancer therapeutic agent for synergistic benefit.

Yet another advantage of the present invention is that the prodrugformulations described herein have reduced the toxicity and/or overcomedifficulties encountered when compared to prior art pharmaceuticalpreparations.

Other and further advantages will be apparent from the followingdescription and drawings.

For purposes of the present invention, the term “residue” shall beunderstood to mean that portion of a compound, to which it refers, i.e.7-ethyl-10-hydroxycamptothecin, amino acid, etc. that remains after ithas undergone a substitution reaction with another compound.

For purposes of the present invention, the term “polymeric containingresidue” or “PEG residue” shall each be understood to mean that portionof the polymer or PEG which remains after it has undergone a reactionwith 7-ethyl-10-hydroxycamptothecin-containing compounds.

For purposes of the present invention, the term “alkyl” as used hereinrefers to a saturated aliphatic hydrocarbon, including straight-chain,branched-chain, and cyclic alkyl groups. The term “alkyl” also includesalkyl-thio-alkyl, alkoxyalkyl, cycloalkylalkyl, heterocycloalkyl, C₁₋₆hydrocarbonyl, groups. Preferably, the alkyl group has 1 to 12 carbons.More preferably, it is a lower alkyl of from about 1 to 7 carbons, yetmore preferably about 1 to 4 carbons. The alkyl group can be substitutedor unsubstituted. When substituted, the substituted group(s) preferablyinclude halo, oxy, azido, nitro, cyano, alkyl, alkoxy, alkyl-thio,alkyl-thio-alkyl, alkoxyalkyl, alkylamino, trihalomethyl, hydroxyl,mercapto, hydroxy, cyano, alkylsilyl, cycloalkyl, cycloalkylalkyl,heterocycloalkyl, heteroaryl, alkenyl, alkynyl, C₁₋₆ hydrocarbonyl,aryl, and amino groups.

For purposes of the present invention, the term “substituted” as usedherein refers to adding or replacing one or more atoms contained withina functional group or compound with one of the moieties from the groupof halo, oxy, azido, nitro, cyano, alkyl, alkoxy, alkyl-thio,alkyl-thio-alkyl, alkoxyalkyl, alkylamino, trihalomethyl, hydroxyl,mercapto, hydroxy, cyano, alkylsilyl, cycloalkyl, cycloalkylalkyl,heterocycloalkyl, heteroaryl, alkenyl, alkynyl, C₁₋₆ hydrocarbonyl,aryl, and amino groups.

The term “alkenyl” as used herein refers to groups containing at leastone carbon-carbon double bond, including straight-chain, branched-chain,and cyclic groups. Preferably, the alkenyl group has about 2 to 12carbons. More preferably, it is a lower alkenyl of from about 2 to 7carbons, yet more preferably about 2 to 4 carbons. The alkenyl group canbe substituted or unsubstituted. When substituted the substitutedgroup(s) preferably include halo, oxy, azido, nitro, cyano, alkyl,alkoxy, alkyl-thio, alkyl-thio-alkyl, alkoxyalkyl, alkylamino,trihalomethyl, hydroxyl, mercapto, hydroxy, cyano, alkylsilyl,cycloalkyl, cycloalkylalkyl, heterocycloalkyl, heteroaryl, alkenyl,alkynyl, C₁₋₆ hydrocarbonyl, aryl, and amino groups.

The term “alkynyl” as used herein refers to groups containing at leastone carbon-carbon triple bond, including straight-chain, branched-chain,and cyclic groups, Preferably, the alkynyl group has about 2 to 12carbons. More preferably, it is a lower alkynyl of from about 2 to 7carbons, yet more preferably about 2 to 4 carbons. The alkynyl group canbe substituted or unsubstituted. When substituted the substitutedgroup(s) preferably include halo, oxy, azido, nitro, cyano, alkyl,alkoxy, alkyl-thio, alkyl thio alkyl, alkoxyalkyl, alkylamino,trihalomethyl, hydroxyl, mercapto, hydroxy, cyano, alkylsilyl,cycloalkyl, cycloalkylalkyl, heterocycloalkyl, heteroaryl, alkenyl,alkynyl, C₁₋₆ hydrocarbonyl, aryl, and amino groups. Examples of“alkynyl” include propargyl, propyne, and 3-hexyne.

The term “aryl” as used herein refers to an aromatic hydrocarbon ringsystem containing at least one aromatic ring. The aromatic ring canoptionally be fused or otherwise attached to other aromatic hydrocarbonrings or non-aromatic hydrocarbon rings. Examples of aryl groupsinclude, for example, phenyl, naphthyl, 1,2,3,4-tetrahydronaphthaleneand biphenyl. Preferred examples of aryl groups include phenyl andnaphthyl.

The term “cycloalkyl” as used herein refers to a C₃₋₈ cyclichydrocarbon. Examples of cycloalkyl include cyclopropyl, cyclobutyl,cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl.

The term “cycloalkenyl” as used herein refers to a C₃₋₈ cyclichydrocarbon containing at least one carbon-carbon double bond. Examplesof cycloalkenyl include cyclopentenyl, cyclopentadienyl, cyclohexenyl,1,3-cyclohexadienyl, cycloheptenyl, cycloheptatrienyl, and cyclooctenyl.

The term “cycloalkylalkyl” as used herein refers to an alklyl groupsubstituted with a C₃₋₈ cycloalkyl group. Examples of cycloalkylalkylgroups include cyclopropylmethyl and cyclopentylethyl.

The term “alkoxy” as used herein refers to an alkyl group of indicatednumber of carbon atoms attached to the parent molecular moiety throughan oxygen bridge. Examples of alkoxy groups include, for example,methoxy, ethoxy, propoxy and isopropoxy.

An “alkylaryl” group as used herein refers to an aryl group substitutedwith an alkyl group.

An “aralkyl” group as used herein refers to an alkyl group substitutedwith an aryl group.

The term “alkoxyalkyl” group as used herein refers to an alkyl groupsubstituted with an alkloxy group.

The term “alkyl-thio-alkyl” as used herein refers to an alkyl-5-alkylthioether, for example methylthiomethyl or methylthioethyl.

The term “amino” as used herein refers to a nitrogen containing group asis known in the art derived from ammonia by the replacement of one ormore hydrogen radicals by organic radicals. For example, the terms“acylamino” and “alkylamino” refer to specific N-substituted organicradicals with acyl and alkyl substituent groups respectively.

The term “alkylcarbonyl” as used herein refers to a carbonyl groupsubstituted with alkyl group.

The terms “halogen’ or “halo” as used herein refer to fluorine,chlorine, bromine, and iodine.

The term “heterocycloalkyl” as used herein refers to a non-aromatic ringsystem containing at least one heteroatom selected from nitrogen,oxygen, and sulfur. The heterocycloalkyl ring can be optionally fused toor otherwise attached to other heterocycloalkyl rings and/ornon-aromatic hydrocarbon rings. Preferred heterocycloalkyl groups havefrom 3 to 7 members. Examples of heterocycloalkyl groups include, forexample, piperazine, morpholine, piperidine, tetrahydrofuran,pyrrolidine, and pyrazole. Preferred heterocycloalkyl groups includepiperidinyl, piperazinyl, morpholinyl, and pyrrolidinyl.

The term “heteroaryl” as used herein refers to an aromatic ring systemcontaining at least one heteroatom selected from nitrogen, oxygen, andsulfur. The heteroaryl ring can be fused or otherwise attached to one ormore heteroaryl rings, aromatic or non-aromatic hydrocarbon rings orheterocycloalkyl rings. Examples of heteroaryl groups include, forexample, pyridine, furan, thiophene, 5,6,7,8-tetrahydroisoquinoline andpyrimidine. Preferred examples of heteroaryl groups include thienyl,benzothienyl, pyridyl, quinolyl, pyrazinyl, pyrimidyl, imidazolyl,benzimidazolyl, furanyl, benzofuranyl, thiazolyl, benzothiazolyl,isoxazolyl, oxadiazolyl, isothiazolyl, benzisothiazolyl, triazolyl,tetrazolyl, pyrrolyl, indolyl, pyrazolyl, and benzopyrazolyl.

The term “heteroatom” as used herein refers to nitrogen, oxygen, andsulfur.

In some embodiments, substituted alkyls include carboxyalkyls,aminoalkyls, dialkylaminos, hydroxyalkyls and mercaptoalkyls;substituted alkenyls include carboxyalkenyls, dialkenylaminos,hydroxyalkenyls and mercaptoalkenyls; substituted alkynyls includecarboxyalkynyls, aminoalkynyls, dialkynylaminos, hydroxyalkynyls andmercaptoalkynyls; substituted cycloalkyls include moieties such as4-chlorocyclohexyl; aryls include moieties such as napthyl; substitutedaryls include moieties such as 3-bromo phenyl; aralkyls include moietiessuch as tolyl; heteroalkyls include moieties such as ethylthiophene;substituted heteroalkyls include moieties such as 3-methoxy-thiophene;alkoxy includes moieties such as methoxy; and phenoxy includes moietiessuch as 3-nitrophenoxy.

For purposes of the present invention, “positive integer” shall beunderstood to include an integer equal to or greater than 1 and as willbe understood by those of ordinary skill to be within the realm ofreasonableness by the artisan of ordinary skill.

The terms “effective amounts” and “sufficient amounts” for purposes ofthe present invention shall mean an amount which achieves a desiredeffect or therapeutic effect as such effect is understood by those ofordinary skill in the art.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows anticancer activity of four-armPEG-Gly-7-ethyl-10-hydroxycamptothecin in treatment of CPT-11 refractorycolorectal tumor as described in Example 1.

FIG. 2 shows anticancer activity of four-armPEG-Gly-7-ethyl-10-hydroxycamptothecin in treatment of CPT-11 refractorycolorectal tumor as described in Example 2.

FIG. 3 shows in vitro cytotoxicity of four-armPEG-Gly-7-ethyl-10-hydroxycamptothecin in the cells refractory to CPT asdescribed in Example 3.

FIG. 4 shows in vitro cytotoxicity of four-armPEG-Gly-7-ethyl-10-hydroxycamptothecin in the cells non-refractory toCPT as described in Example 3.

DETAILED DESCRIPTION OF INVENTION A. Overview

In one aspect of the present invention, there are provided methods oftreating a resistant or refractory cancer in a mammal, comprising:

administering an effective amount of a compound of formula (I):

wherein

R₃, R₂, R₃ and R₄ are independently OH or

-   -   wherein    -   L is a bifunctional linker;    -   m is 0 or a positive integer, preferably 1; and    -   n is a positive integer;    -   provided that R₁, R₂, R₃ and R₄ are not all OH;        or a pharmaceutically acceptable salt thereof to the mammal in        need thereof.

In an alternative embodiment, one, two or three of R₁, R₂, R₃ and R₄ canbe CH₃.

For purposes of the present invention, refractory or resistant cancersare defined as cancers that do not respond to previous anticancertherapy or treatment. In one preferred aspect, the cancers arerefractory or resistant to CPT-11 treatment. The cancers can beresistant or refractory at the beginning of treatment, or they maybecome resistant or refractory during treatment. Refractory cancersinclude tumors that do not respond at the onset of treatment or respondinitially for a short period but fail to respond to treatment.Refractory cancers also include tumors that respond to treatment withanticancer therapy but fail to respond to subsequent rounds oftherapies. For purposes of this invention, refractory cancers alsoencompass tumors that appear to be inhibited by treatment withanticancer therapy but recur up to five years, sometimes up to ten yearsor longer after treatment is discontinued. The anticancer therapy canemploy chemotherapeutic agents alone, radiation alone or combinationsthereof. For ease of description and not limitation, it will beunderstood that the refractory cancers are interchangeable withresistant cancers.

For purposes of the present invention, successful treatment of aresistant or refractory cancer shall be understood to mean thatresistant or refractory symptoms or conditions are prevented, minimizedor attenuated during and/or after anticancer treatment, when compared tothat observed in the absence of the treatment described herein. Theminimized, attenuated or prevented refractory conditions can beconfirmed by clinical markers contemplated by the artisan in the field.In one example, successful treatment of refractory or resistant cancershall be deemed to occur when at least 5% or preferably 10%, morepreferably 20% or higher (i.e., 30, 40, 50% or more) inhibition ordecrease in tumor growth and/or recurrence including other clinicalmarkers contemplated by the artisan in the field is realized whencompared to that observed in the absence of the treatment describedherein. Clinical markers which show changes in the severity andmagnitude of the refractory cancers can be determined by clinicians. Insome aspects, the resistant or refractory cancers can be one or more ofthe following: solid tumors, lymphomas, small cell lung cancer, acutelymphocytic leukemia (ALL), pancreatic cancer, glioblastoma, ovariancancer, gastric cancers, etc. The methods are useful for, among otherthings, treating neoplastic disease, reducing tumor burden, preventingmetastasis of neoplasms and preventing recurrences of tumor/neoplasticgrowths in mammals. In certain aspect, the resistant or refractorycancers are solid tumors or metastatic cancers. In one particularaspect, the resistant or refractory cancer is colorectal cancer.

The present invention provides methods of treating resistant orrefractory cancers to chemotherapy. In one preferred aspect, the presentinvention provides methods of treating cancers which are resistant orrefractory to camptothecin (CPT) or camptothecin analog therapy.Alternatively, the methods described herein can be effective to treatcancers resistant or refractory to CPT or CPT analog conjugated topolymers such as polyethylene glycol. In more preferred aspect, thepresent invention provides methods of treating cancers which areresistant or refractory to camptothecin or CPT-11 therapy.

Camptothecin and certain related analogs share the structure:

From this core structure, several known analogs have been prepared. Forexample, the A ring in either or both of the 10- and 11-positions can besubstituted with an OH. The A ring can also be substituted with astraight or branched C₁₋₃₀ alkyl or C₁₋₁₇ alkoxy, optionally linked tothe ring by a heteroatom i.e. —O or —S. The B ring can be substituted inthe 7-position with a straight or branched C₁₋₃₀ alkyl (preferably C₂alkyl), C₅₋₈ cycloakyl, C₁₋₃₀ alkoxy, phenyl alkyl, etc., alkylcarbamate, alkyl carbazides, phenyl hydrazine derivatives, etc. Othersubstitutions are possible in the C, D and E rings. See, for example,U.S. Pat. Nos. 5,004,758; 4,943,579; 4,473,692; RE32,518, the contentsof which are incorporated herein by reference. The10-hydroxycamptothecin, 11-hydroxycamptothecin and the10,11-dihydroxycamtothecin analogs occur naturally as one of the minorcomponents in C. Acuminata and its relatives. Additional substitutionsto these compounds, i.e. 7-alkyl-, 7-substituted alkyl-, 7-amino-,7-aminoalkyl-, 7-aralkyl-, 9-alkyl-, 9-aralkyl-camptothecin etc.derivatives are made using known synthetic techniques. Some camptothecaalkaloids have the structure shown below:

In the structure shown above, R₇ is one of NO₂, NH₂, N₃, hydrogen,halogen (F, Cl, Br, I), COOH, OH, O—C₁₋₈ alkyl, SH, S—C₁₋₃ alkyl, CN,CH₂NH₂, NH—C₁₋₃ alkyl, CH₂—NH—C₁₋₃ alkyl, N(C₁₋₃ alkyl)₂,CH₂N(C₁₋₃alkyl), O—, NH— and S—CH₂CH₂N(CH₂CH₂OH)₂, O—, NH— andS—CH₂CH₂CH₂N(CH₂CH₂OH)₂, O—, NH— and S—CH₂CH₂N(CH₂CH₂CH₂OH)₂, O—, NH—and S—CH₂CH₂CH₂N(CH₂CH₂CH₂OH₂)₂, O—, NH— and S—CH₂CH₂N(C₁₋₃ alkyl)₂, O—,NH— and S—CH₂CH₂CH₂N(C₁₋₃ alkyl)₂, CHO or C₁₋₃ alkyl.

R₈ in the structure (II) shown above can be H or C₁₋₈ alkyl (preferablyC₂ alkyl) or CH₂NR₉R₁₀ where

-   -   (a) R₉ and R₁₀ are, independently, hydrogen, C₁₋₆ alkyl, C₃₋₇        cycloalkyl, C₃₋₇ cycloalkyl-C₁₋₆ alkyl, C₂₋₆ alkenyl,        hydroxy-C₁₋₆ alkyl, C₁₋₆ alkoxy-C₁₋₆ alkyl; alternatively    -   (b) R₉ can be hydrogen, C₁₋₆ alkyl, C₃₋₇ cycloalkyl, C₃₋₇        cycloalkyl-C₁₋₆ alkyl, C₂₋₆ alkenyl, hydroxy-C₁₋₆ alkyl, C₁₋₆        alkoxy-C₁₋₆ alkyl and R₁₀ can be —COR₁₁ where R₁₁ is hydrogen,        C₁₋₆ alkyl, perhalo-C₁₋₆ alkyl, C₃₋₇ cycloalkyl, C₃₋₇        cycloalkyl-C₁₋₆ alkyl, C₂₋₆ alkenyl, hydroxy-C₁₋₆ alkyl, C₁₋₆        alkoxy, C₁₋₆ alkoxy-C₁₋₆ alkyl; or    -   (c) R₉ and R₁₀ taken together with the nitrogen atom to which        they are attached form a saturated 3-7 membered heterocyclic        ring which may contain a O, S or NR₁₂ group, where R₁₂ is        hydrogen, C₁₋₆ alkyl, perhalo-C₁₋₆ alkyl, aryl, aryl substituted        with one or more groups selected from among C₁₋₆ alkyl, halogen,        nitro, amino, C₁₋₆ alkylamino, perhalo-C₁₋₆ alkyl, hydroxy-C₁₋₆        alkyl, C₁₋₆ alkoxy, C₁₋₆ alkoxy-C₁₋₆ alkyl and —COR₁₃ where R₁₃        is hydrogen, C₁₋₆ alkyl, perhalo-C₁₋₆ alkyl, C₁₋₆ alkoxy, aryl,        and aryl substituted with one or more of C₁₋₆ alkyl,        perhalo-C₁₋₆ alkyl, hydroxy-C₁₋₆ alkyl, or C₁₋₆ alkoxy-C₁₋₆        alkyl groups;    -   R₁₁₀-R₁₁₁ are each independently selected from among hydrogen;        halo; acyl; alkyl (e.g., C₁₋₆ alkyl); substituted alkyl; alkoxy        (e.g., C₁₋₆ alkoxy); substituted alkoxy; alkenyl; alkynyl;        cycloalkyl; hydroxyl; cyano; nitro; azido; amido; hydrazine;        amino; substituted amino (e.g., monoalkylamino and        dialkylamino); hydroxcarbonyl; alkoxycarbonyl; alkylcarbonyloxy;        alkylcarbonylamino; carbamoyloxy; arylsulfonyloxy;        alkylsulfonyloxy; —C(R₁₁₇)═N—(O)_(j)—R₁₁₈ wherein R₁₁₇ is H,        alkyl, alkenyl, cycloalkyl, or aryl, j is 0 or 1, and R₁₁₈ is H,        alkyl, alkenyl, cycloalkyl, or heterocycle; and R₁₁₉C(O)O—        wherein R₁₁₉ is halogen, amino, substituted amino, heterocycle,        substituted heterocycle, or R₁₂₀—O—(CH₂)_(k)— where k is an        integer of 1-10 and R₁₂₀ is alkyl, phenyl, substituted phenyl,        cycloalkyl, substituted cycloalkyl, heterocycle, or substituted        heterocycle; or

R₇ together with R₁₁₀ or R₁₁₀ together with R₁₁₁ form substituted orunsubstituted methylenedioxy, ethylenedioxy, or ethyleneoxy; and

R₁₁₂ is H or OR′, wherein R′ is alkyl, alkenyl, cycloalkyl, haloalkyl,or hydroxyalkyl.

The aryl groups can be phenyl and naphthyl. Suitable heterocyclic ringswhen R₉ and R₁₀ are taken together with the nitrogen atom to which theyare attached include: aziridine, azetidine, pyrrolidine, piperidine,hexamethylenimine, imidazolidine, pyrazolidine, isoxazolidine,piperazine, N-methylpiperazine, tetrahydroazepine,N-methyl-tetrahydroazepine, thiazolidine, etc.

In alternative aspects of the invention, the treatment of the presentinvention includes administering an effective amount of the compoundsdescribed herein to a mammal with resistant or refractory cancersshowing topoisomerase I mediated resistance or refractory phenomenon.

In yet alternative aspects, the present invention provides methods oftreating resistant or refractory cancers associated with radiationtherapy alone or radiation therapy in combination with a secondchemotherapy. Standard protocols of radiation therapy are well known inthe art and thus, the combination therapy using the compounds describedherein can be done without undue experimentation.

In still another aspect, the treatment of the present invention includesadministering an effective amount of the compounds described hereinalone or in combination, simultaneously or sequentially, with a secondchemotherapeutic agent. The multi-arm polymeric prodrugs of7-ethyl-10-hydroxycamptothecin can be administered concurrently with thechemotherapeutic agent or after the administration of thechemotherapeutic agent. Thus, the compounds employed in the presentinvention can be administered during or after treatment of the secondchemotherapeutic agent.

For example, a non-liming list of the second chemotherapeutic agentsincludes:

(i) DNA topoisomerase inhibitor: adriamycin, amsacrine, camptothecin,CPT-11, daunorubicin, dactinomycin, doxorubicin, eniposide, epirubicin,etoposide, idarubicin, or mitoxantrone;

(ii) microtubule inhibiting drug, such as a taxane, includingpaclitaxel, docetaxel, vincristin, vinblastin, nocodazole, epothilonesand navelbine;

(iii) DNA damaging agent: actinomycin, amsacrine, anthracyclines,bleomycin, busulfan, camptothecin, carboplatin, chlorambucil, cisplatin,cyclophosphamide, cytoxan, dactinomycin, daunorubicin, docetaxel,doxorubicin, epirubicin, hexamethylmelamineoxaliplatin, iphosphamide,melphalan, merchlorehtamine, mitomycin, mitoxantrone, nitrosourea,plicamycin, procarbazine, taxol, taxotere, teniposide,triethylenethiophosphoramide or etoposide (VP 16);

(iv) antimetabolite: folate antagonist; and

(v) nucleoside analog: 5-fluorouracil; cytosine arabinoside,azacitidine, 6-mercaptopurine, azathioprine; 5-iodo-2′-deoxyuridine;6-thioguanine, 2-deoxycoformycin, cladribine, cytarabine, fludarabine,mercaptopurine, thioguanine, pentostatin, AZT (zidovudine), ACV,valacylovir, famiciclovir, acyclovir, cidofovir, penciclovir,ganciclovir, Ribavirin, ddC, ddI (zalcitabine), lamuvidine, Abacavir,Adefovir, Didanosine, d4T (stavudine), 3TC, BW 1592, PMEA/bis-POM PMEA,ddT, HPMPC, HPMPG, HPMPA, PMEA, PMEG, dOTC; DAPD, Ara-AC, pentostatin,dihydro-5-azacytidine, tiazofurin, sangivamycin, Ara-A (vidarabine),6-MMPR, 5-FUDR (floxuridine), cytarabine (Ara-C; cytosine arabinoside),5-azacytidine (azacitidine), HBG [9-(4-hydroxybutyl)guanine],(1S,4R)-4-[2-amino-6-cyclopropyl-amino)-9H-purin-9-yl]-2-cyclopentene-1-m-ethanolsuccinate (“159U89”), uridine, thymidine, idoxuridine, 3-deazauridine,cyclocytidine, dihydro-5-azacytidine, triciribine, ribavirin,fludrabine, Acyclovir,1-beta-D-arabinofuranosyl-E-5-(2-bromovinyl)uracil,2′-fluorocarbocyclic-2′-deoxyguanosine;6′-fluorocarbocyclic-2′-deoxyguanosine;1-(beta-D-arabinofuranosyl)-5(E)-(2-iodovinyl)uracil; {(1r-1 alpha,2beta,3alpha)-2-amino-9-(2,3-bis(hydroxymethyl)cyclobut-yl)-6H-purin-6-one}Lobucavir,9H-purin-2-amine,9-((2-(1-methylethoxy)-1-((1-methylethoxy)-methyl)ethoxy)methyl)-(9Cl);trifluorothymidine, 9->(1,3-dihydroxy-2-propoxy)-methylguanine(ganciclovir), 5-ethyl-2′-deoxyuridine;E-5-(2-bromovinyl)-2′-deoxyuridine; 5-(2-chloroethyl)-2′-deoxyuridine,buciclovir, 6-deoxyacyclovir;9-(4-hydroxy-3-hydroxymethylbut-1-yl)guanine,E-5-(2-iodovinyl)-2′-deoxyuridine, arabinofuranosyluracil,1-β-D-arabinofuranosylthymine; 2′-nor-2′ deoxyguanosine; and1-β-D-arabinofuranosyladenine.

Other potential anti-cancer agents are selected from altretamine,aminoglutethimide, amsacrine, anastrozole, asparaginase, beg,bicalutamide, bleomycin, buserelin, busulfan, calcium folinate,campothecin, capecitabine, carboplatin, carmustine, chlorambucil,cisplatin, cladribine, clodronate, colchicine, crisantaspase,cyclophosphamide, cyproterone, cytarabine, dacarbazine, dactinomycin,daunorubicin, dienestrol, diethylstilbestrol, docetaxel, doxorubicin,epirubicin, estradiol, estramustine, etoposide, exemestane, filgrastim,fludarabine, fludrocortisone, fluorouracil, fluoxymesterone, flutamide,gemcitabine, genistein, goserelin, hydroxyurea, idarubicin, ifosfamide,iniatinib, interferon, irinotecan, ironotecan, letrozole, leucovorin,leuprolide, levamisole, lomustine, mechlorethamine, medroxyprogesterone,megestrol, melphalan, mercaptopurine, mesna, methotrexate, mitomycin,mitotane, mitoxantrone, nilutamide, nocodazole, octreotide, oxaliplatin,paclitaxel, pamidronate, pentostatin, plicamycin, porfimer,procarbazine, raltitrexed, rituximab, streptozocin, suramin, tamoxifen,temozolomide, teniposide, testosterone, thioguanine, thiotepa,titanocene dichloride, topotecan, trastuzumab, tretinoin, vinblastine,vincristine, vindesine, and vinorelbine. Other numerous anti-canceragents are listed in US Patent Publication No. 2006/0135468, thecontents of which are incorporated herein by reference. As will beappreciated by those of ordinary skill, the amount and protocol fordelivering the second chemotherapeutic agent can vary greatly dependingupon the condition being treated and the recognized acceptable amountsand dosing of the secondary chemotherapeutic agents. The range of dosagefor such secondary agents does not require undue experimentation forsuccessful implementation by the artisan of ordinary skill.

In certain embodiment of the present invention, the treatment ofresistant or refractory cancers uses the compounds among:

One particularly preferred compound is

wherein all four arms of the polymer are conjugated to7-ethyl-10-hydroxycamptothecin through glycine and n is from about 28 toabout 341, preferably from about 114 to about 227, or more preferablyabout 227. One preferred embodiment (compound 9) of the presentinvention has a molecular weight of about 40,000 da and have thestructure of:

Without being bound by any theory, it is believed that the unexpectedefficacy of the methods described herein in treatment of CPT-11refractory tumors can be attributed, at least in part, to the favorablepharmacokinetic and biodistribution properties of the polymericcompounds described herein. The unexpected efficacy of the compoundsdescribed herein can also be based in part on a novel mechanism ofaction for the drug in vivo. It has been reported that topotecan,another TOP1 inhibitor, inhibits hypoxia-inducible factor (HIF)-1α,leading to marked decrease of angiogenesis and significant tumor growthinhibition. Consistent with this observation, it is believed that theinventive treatment induces a decrease in HIF-1α in cells, which thenaccumulate the compounds described herein due to an EPR effect in CPT-11refractory (or sensitive) tumors. However, it is believed that CPT-11fails to induce a decrease in HIF-1α in CPT-11 refractory tumors,leading to even more angiogenesis. In this aspect, treatment of highlyvascular tumors can benefit from accumulation of the inventive compoundsdescribed herein due to enhanced EPR effects.

It has also been reported that CPT-11 resistant tumors may have lowerlevels of TOP1, since low levels of TOP1 have been linked to CPT-11resistance in tissue culture. The polymeric ester derivatives of7-ethyl-10-hyroxycamptothecin according to the therapy described hereincan also provide higher exposure of 7-ethyl-10-hyroxycamptothecin tocells in vivo than CPT-11. Drug concentrations can be sufficient to killcells even with low levels of TOP1. Alternatively, variable levels ofcarboxylesterase can be another contributing factor to CPT-11resistance, and this enzyme is not required for release of7-ethyl-10-hyroxycamptothecin from the polymeric ester derivatives of7-ethyl-10-hyroxycamptothecin conjugates described herein.

B. Multi-Arm Polymeric Conjugates of 7-Ethyl-10-Hydroxy-Camptothecin

1. Multi-Arm Polymers

The polymeric prodrugs of 7-ethyl-10-hydroxycamptothecin includefour-arm PEG attached to 20-OH group of 7-ethyl-10-hydroxycamptothecinthrough a bifunctional linker. In one aspect of the present invention,the polymeric prodrugs of 7-ethyl-10-hydroxy-camptothecin includefour-arm PEG, prior to conjugation, having the following structure of

wherein n is a positive integer.The polymers are those described in NOF Corp. Drug Delivery Systemcatalog, Ver. 8, April 2006, the disclosure of which is incorporatedherein by reference.

In one preferred embodiment of the invention, the degree ofpolymerization for the polymer (n) is from about 28 to about 341 toprovide polymers having a total molecular weight of from about 5,000 Dato about 60,000 Da, and preferably from about 114 to about 227 toprovide polymers having a total molecular weight of from 20,000 Da to40,000 Da. (n) represents the number of repeating units in the polymerchain and is dependent on the molecular weight of the polymer. In oneparticularly preferred embodiment of the invention, n is about 227 toprovide the polymeric portion having a total molecular weight of about40,000 Da.

2. Bifunctional Linkers

In certain aspects of the present invention, L is a residue of an aminoacid. The amino acid can be selected from any of the knownnaturally-occurring L-amino acids, e.g., alanine, valine, leucine,isoleucine, glycine, serine, threonine, methionine, cysteine,phenylalanine, tyrosine, tryptophan, aspartic acid, glutamic acid,lysine, arginine, histidine, proline, and/or a combination thereof, toname but a few. In alternative aspects, L can be a peptide residue. Thepeptide can range in size, for instance, from about 2 to about 10 aminoacid residues.

Derivatives and analogs of the naturally occurring amino acids, as wellas various art-known non-naturally occurring amino acids (D or L),hydrophobic or non-hydrophobic, are also contemplated to be within thescope of the invention. Simply by way of example, amino acid analogs andderivates include:

-   2-aminoadipic acid, 3-aminoadipic acid, beta-alanine,    beta-aminopropionic acid,-   2-aminobutyric acid, 4-aminobutyric acid, piperidinic acid,    6-aminocaproic acid,-   2-aminoheptanoic acid, 2-aminoisobutyric acid, 3-aminoisobutyric    acid,-   2-aminopimelic acid, 2,4-aminobutyric acid, desmosine,    2,2-diaminopimelic acid,-   2,3-diaminopropionic acid, n-ethylglycine, N-ethylasparagine,    3-hydroxyproline,-   4-hydroxyproline, isodesmosine, allo-isoleucine, N-methylglycine or    sarcosine,-   N-methyl-isoleucine, 6-N-methyllysine, N-methylvaline, norvaline,    norleucine, ornithine,    and others too numerous to mention, that are listed in 63 Fed. Reg.,    29620, 29622, incorporated by reference herein. Some preferred L    groups include glycine, alanine, methionine or sarcosine residues.    For example, the compounds can be among:

For ease of the description and not limitation, one arm of the four-armPEG is shown. One arm, up to four arms of the four-arm PEG can beconjugated with 7-ethyl-10-hydroxy-camptothecin.

More preferably, compounds of the present invention include a glycineresidue as the linker group (L).

Alternatively, L after attachment between the camptothecin analog andpolymer is selected among:

—[C(═O)]_(v)(CR₂₂R₂₃)_(t)—,

—[C(═O)]_(v)(CR₂₂R₂₃)_(t)—O—,

—[C(═O)]_(v)(CR₂₂R₂₃)_(t)—NR₂₆—,

—[C(═O)]_(v)O(CR₂₂R₂₃)_(t)—,

—[C(═O)]_(v)O(CR₂₂R₂₃)_(t)O—,

—[C(═O)]_(v)O(CR₂₂R₂₃)_(t)NR₂₆—,

—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)—,

—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)O—,

—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)NR₂₆—,

—[C(═O)]_(v)(CR₂₂R₂₃O)_(t)—,

—[C(═O)]_(v)O(CR₂₂R₂₃O)_(t)—,

—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃O)_(t)—,

—[C(═O)]_(v)(CR₂₂R₂₃O)_(t)(CR₂₄R₂₅)_(y)—,

—[C(═O)]_(v)O(CR₂₂R₂₃O)_(t)(CR₂₄R₂₅)_(Y)—,

—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃O)_(t)(CR₂₄R₂₅)_(y)—,

—[C(═O)]_(v)(CR₂₂R₂₃O)_(t)(CR₂₄R₂₅)_(y)O—,

—[C(═O)]_(v)(CR₂₂R₂₃)_(t)(CR₂₄R₂₅O)_(y)—,

—[C(═O)]_(v)O(CR₂₂R₂₃O)_(t)(CR₂₄R₂₅)_(y)O—,

—[C(═O)]_(v)O(CR₂₂R₂₃)_(t)(CR₂₄R₂₅O)_(y)—,

—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃O)_(t)(CR₂₄R₂₅)_(y)O—,

—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)(CR₂₄R₂₅O)_(y)—,

—[C(═O)]_(v)(CR₂₂R₂₃)_(t)O—(CR₂₈R₂₉)_(t′)—,

—[C(═O)]_(v)(CR₂₂R₂₃)_(t)NR₂₆—(CR₂₈R₂₉)_(t′)—,

—[C(═O)]_(v)(CR₂₂R₂₃)_(t)S—(CR₂₈R₂₉)_(t′)—,

—[C(═O)]_(v)O(CR₂₂R₂₃)_(t)O—(CR₂₈R₂₉)_(t′)—,

—[C(═O)]_(v)O(CR₂₂R₂₃)_(t)NR₂₆—(CR₂₈R₂₉)_(t′)—,

—[C(═O)]_(v)O(CR₂₂R₂₃)_(t)S—(CR₂₈R₂₉)_(t′)—,

—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)O—(CR₂₈R₂₉)_(t′)—,

—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)NR₂₆—(CR₂₈R₂₉)_(t′)—,

—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)S—(CR₂₈R₂₉)_(t′)—,

—[C(═O)]_(v)(CR₂₂R₂₃CR₂₈R₂₉O)_(t)NR₂₆—,

—[C (═O)]_(v)(CR₂₂R₂₃CR₂₈R₂₉O)_(t)—,

—[C(═O)]_(v)O(CR₂₂R₂₃CR₂₈R₂₉O)_(t)NR₂₆—,

—[C(═O)]_(v)O(CR₂₂R₂₃CR₂₈R₂₉O)_(t)—,

—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃CR₂₈R₂₉O)_(t)NR₂₆—,

—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃CR₂₈R₂₉O)_(t)—,

—[C(═O)]_(V)(CR₂₂R₂₃CR₂₈R₂₉O)_(t)(CR₂₄R₂₅)_(y)—,

—[C(═O)]_(v)O(CR₂₂R₂₃CR₂₈R₂₉O)_(t)(CR₂₄R₂₅)_(y)—,

—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃CR₂₈R₂₉O)_(t)(CR₂₄R₂₅)_(y)—,

—[C(═O)]_(v)(CR₂₂R₂₃CR₂₈R₂₉O)_(t)(CR₂₄R₂₅)_(y)O—,

—[C(═O)]_(v)(CR₂₂R₂₃)_(t)(CR₂₄R₂₅CR₂₈R₂₉O)_(y)—,

—[C(═O)]_(v)(CR₂₂R₂₃)_(t)(CR₂₄R₂₅CR₂₈R₂₉O)_(y)NR₂₆—,

—[C(═O)]_(v)O(CR₂₂R₂₃CR₂₈R₂₉O)_(t)(CR₂₄R₂₅)_(y)O—,

—[C(═O)]_(v)O(CR₂₂R₂₃)_(t)(CR₂₄R₂₅CR₂₈R₂₉O)_(y)—,

—[C(═O)]_(v)O(CR₂₂R₂₃)_(t)(CR₂₄R₂₅CR₂₈R₂₉O)_(y)NR₂₆—,

—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃CR₂₈R₂₉O)_(t)(CR₂₄R₂₅)_(y)O—,

—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)(CR₂₄R₂₅CR₂₄R₂₅CR₂₈R₂₉O)_(y)—,

—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)(CR₂₄R₂₅CR₂₈R₂₉O)_(y)NR₂₆—,

wherein:

R₂₁-R₂₉ are independently selected among hydrogen, amino, substitutedamino, azido, carboxy, cyano, halo, hydroxyl, nitro, silyl ether,sulfonyl, mercapto, C₁₋₆ alkylmercapto, arylmercapto, substitutedarylmercapto, substituted

C₁₋₆ alkylthio, C₁₋₆ alkyls, C₂₋₆ alkenyl, C₂₋₆ alkynyl, C₃₋₁₉ branchedalkyl, C₃₋₈ cycloalkyl, C₁₋₆ substituted alkyl, C₂₋₆ substitutedalkenyl, C₂₋₆ substituted alkynyl, C₃₋₈ substituted cycloalkyl,substituted aryl, heteroaryl, substituted heteroaryl, C₁₋₆ heteroalkyl,substituted C₁₋₆heteroalkyl, C₁₋₆ alkoxy, aryloxy, C₁₋₆heteroalkoxy,heteroaryloxy, C₂₋₆ alkanoyl, arylcarbonyl, C₂₋₆ alkoxycarbonyl,aryloxycarbonyl, C₂₋₆ alkanoyloxy, arylcarbonyloxy, C₂₋₆ substitutedalkanoyl, substituted arylcarbonyl, C₂₋₆ substituted alkanoyloxy,substituted aryloxycarbonyl, C₂₋₆ substituted alkanoyloxy, substitutedand arylcarbonyloxy;

(t), (t′) and (y) are independently selected from zero or a positiveinteger, preferably from about 1 to about 10; and

(v) is 0 or 1.

In some preferred embodiments, L can include:

—[C(═O)]_(v)(CH₂)_(t)—,

—[C(═O)]_(v)(CH₂)_(t)—O—,

—[C(═O)]_(v)(CH₂)_(t)—NR₂₆—,

—[C(═O)]_(v)O(CH₂)_(t)—,

—[C(═O)]_(v)O(CH₂)_(t)O—,

—[C(═O)]_(v)O(CH₂)NH—,

—[C(═O)]_(v)NH(CH₂)_(t)—,

—[C(═O)]_(v)NH(CH₂)_(t)O—,

—[C(═O)]_(v)NH(CH₂)_(t)NH—,

—[C(═O)]_(v)(CH₂O)_(t)—,

—[C(═O)]_(v)O(CH₂O)_(t)—,

—[C(═O)]_(v)NH(CH₂O)_(t)—,

—[C(═O)]_(v)(CH₂O)_(t)(CH₂)_(y)—,

—[C(═O)]_(v)O(CH₂O)_(t)H₂)_(y)—,

—[C(═O)]_(v)NH(CH₂O)_(t)(CH₂₅)_(y)—,

—[C(═O)]_(v)(CH₂O)_(t)(CH₂)_(y)O—,

—[C(═O)]_(v)(CH₂)_(t)(CH₂O)_(y)—,

—[C(═O)]_(v)O(CH₂O)_(t)(CH₂)_(y)O—,

—[C(═O)]_(v)O(CH₂)_(t)(CH₂O)_(y)—,

—[C(═O)]_(v)NH(CH₂O)_(t)(CH₂)_(y)O—,

—[C (═O)]_(v)NH(CR₂₂R₂₃)_(t)(CH₂O)_(y)—,

—[C(═O)]_(v)(CH₂)_(t)O—(CH₂)_(t′)—,

—[C(═O)]_(v)(CH₂)_(t)NH—(CH₂)_(t′)—,

—[C(═O)]_(v)(CH₂)_(t)S—(CH₂)_(t′)—,

—[C(═O)]_(v)O(CH₂)_(t)O—(CH₂)_(t′)—,

—[C(═O)]vO(CH₂)_(t)NH—(CH₂)_(t′)—,

—[C(═O)]_(v)O(CH₂)_(t)S—(CH₂)_(t′)—,

—[C(═O)]_(v)NH(CR₂₂R₂₃)_(t)O—(CH₂)_(t′)—,

—[C(═O)]_(v)NH(CH₂)_(t)NH—(CH₂)_(t′)—,

—[C(═O)]_(v)NH(CH₂)_(t)S—(CH₂)_(t′)—,

—[C(═O)]_(v)(CH₂CH₂O)_(t)NR₂₆—,

—[C(═O)]_(v)(CH₂CH₂O)_(t)—,

—[C(═O)]_(v)—O—(CH₂CH₂O)_(t)NH—,

[C(═O)]_(v)—O—(CH₂CH₂O)_(t)—,

—[C(═C)]_(v)NH(CH₂CH₂O)_(t)NH—,

—[C(═O)]_(v)NH(CH₂CH₂O)_(t)—,

—[C(═O)]_(v)(CH₂CH₂O)_(t)(CH₂)_(y)—,

—[C(═O)]_(v)O(CH₂CH₂O)_(t)(CH₂)_(y)—,

—[C(═O)]_(v)NH(CH₂CH₂O)_(t)(CH₂)_(y)—,

—[C(═O)]_(v)(CH₂CH₂O)_(t)(CH₂)_(y))—,

—[C(═O)]_(v)(CH₂)_(t)(CH₂CH₂O)_(y)—,

—[C(═O)]_(v)(CH₂)_(t)(CH₂CH₂O)_(y)NH—,

—[C(═O)]_(v)O(CH₂CH₂O)_(t)(CH₂)_(y)O—,

—[C(═O)]_(v)O(CH₂)_(t)(CH₂CH₂O)_(y)—,

—[C(═O)]_(v)O(CH₂)_(t)(CH₂CH₂O)_(y)NH—,

—[C(═O)]_(v)NH(CH₂CH₂O)_(t)(CH₂)_(y)O—,

—[C(═O)]_(v)NH(CH₂)_(t)(CH₂CH₂O)_(y)—,

—[C(O)]_(v)NH(CH₂)_(t)(CH₂CH₂O)_(y)NH—,

wherein (t), (t′) and (y) are independently selected from zero or apositive integer, preferably from about 1 to about 10; and

(v) is 0 or 1.

In some aspects of the present invention, the compounds include from 1to about 10 units of the bifunctional linker. In some preferred aspectsof the present invention, the compounds include one unit of thebifunctional linker and thus m is 1.

Additional linkers are found in Table 1 of Greenwald et al. (Bioorganic& Medicinal Chemistry, 1998, 6:551-562), the contents of which areincorporated by reference herein.

C. Synthesis of Prodrugs

Generally, the polymeric 7-ethyl-10-hydroxycamptothecin prodrugsdescribed herein are prepared by reacting one or more equivalents of anactivated multi-arm polymer with, for example, one or more equivalentsper active site of amino acid-(20)-7-ethyl-10-hydroxycamptothecincompound under conditions which are sufficient to effectively cause theamino group to undergo a reaction with the carboxylic acid of thepolymer and form a linkage. Details of the synthesis are described inU.S. patent application Ser. No. 11/704,607 entitled “Multi-armPolymeric Conjugates of 7-Ethyl-10-hydroxycamptothecin For Treatment ofBreast, Colorectal, Pancreatic, Ovarian and Lung Cancers”, the contentsof which are incorporated herein by reference in its entirety. HPLCanalysis of compounds made in accordance with the methods of synthesisshowed that on average, four 7-ethyl-10-hydroxycamptothecin moleculesare conjugated to one four-arm PEG molecule (4% by weight).

D. Compositions/Formulations

Pharmaceutical compositions containing the polymer conjugates of thepresent invention may be manufactured by processes well known in theart, e.g., using a variety of well-known mixing, dissolving,granulating, levigating, emulsifying, encapsulating, entrapping orlyophilizing processes. The compositions may be formulated inconjunction with one or more physiologically acceptable carrierscomprising excipients and auxiliaries which facilitate processing of theactive compounds into preparations which can be used pharmaceutically.Proper formulation is dependent upon the route of administration chosen.Parenteral routes are preferred in many aspects of the invention.

For injection, including, without limitation, intravenous, intramuscularand subcutaneous injection, the compounds of the invention may beformulated in aqueous solutions, preferably in physiologicallycompatible buffers such as physiological saline buffer or polar solventsincluding, without limitation, a pyrrolidone or dimethylsulfoxide.

The compounds are preferably formulated for parenteral administration,e.g., by bolus injection or continuous infusion. Formulations forinjection may be presented in unit dosage form, e.g., in ampoules or inmulti-dose containers. Useful compositions include, without limitation,suspensions, solutions or emulsions in oily or aqueous vehicles, and maycontain adjuncts such as suspending, stabilizing and/or dispersingagents. Pharmaceutical compositions for parenteral administrationinclude aqueous solutions of a water soluble form, such as, withoutlimitation, a salt of the active compound. Additionally, suspensions ofthe active compounds may be prepared in a lipophilic vehicle. Suitablelipophilic vehicles include fatty oils such as sesame oil, syntheticfatty acid esters such as ethyl oleate and triglycerides, or materialssuch as liposomes. Aqueous injection suspensions may contain substancesthat increase the viscosity of the suspension, such as sodiumcarboxymethyl cellulose, sorbitol, or dextran. Optionally, thesuspension may also contain suitable stabilizers and/or agents thatincrease the solubility of the compounds to allow for the preparation ofhighly concentrated solutions. Alternatively, the active ingredient maybe in powder form for constitution with a suitable vehicle, e.g.,sterile, pyrogen-free water, before use.

For oral administration, the compounds can be formulated by combiningthe active compounds with pharmaceutically acceptable carrierswell-known in the art. Such carriers enable the compounds of theinvention to be formulated as tablets, pills, lozenges, dragees,capsules, liquids, gels, syrups, pastes, slurries, solutions,suspensions, concentrated solutions and suspensions for diluting in thedrinking water of a patient, premixes for dilution in the feed of apatient, and the like, for oral ingestion by a patient. Pharmaceuticalpreparations for oral use can be made using a solid excipient,optionally grinding the resulting mixture, and processing the mixture ofgranules, after adding other suitable auxiliaries if desired, to obtaintablets or dragee cores. Useful excipients are, in particular, fillerssuch as sugars, including lactose, sucrose, mannitol, or sorbitol,cellulose preparations such as, for example, maize starch, wheat starch,rice starch and potato starch and other materials such as gelatin, gumtragacanth, methyl cellulose, hydroxypropyl-methylcellulose, sodiumcarboxy-methylcellulose, and/or polyvinylpyrrolidone (PVP). If desired,disintegrating agents may be added, such as cross-linked polyvinylpyrrolidone, agar, or alginic acid. A salt such as sodium alginate mayalso be used.

For administration by inhalation, the compounds of the present inventioncan conveniently be delivered in the form of an aerosol spray using apressurized pack or a nebulizer and a suitable propellant.

The compounds may also be formulated in rectal compositions such assuppositories or retention enemas, using, e.g., conventional suppositorybases such as cocoa butter or other glycerides.

In addition to the formulations described previously, the compounds mayalso be formulated as depot preparations. Such long acting formulationsmay be administered by implantation (for example, subcutaneously orintramuscularly) or by intramuscular injection. The compounds of thisinvention may be formulated for this route of administration withsuitable polymeric or hydrophobic materials (for instance, in anemulsion with a pharmacologically acceptable oil), with ion exchangeresins, or as a sparingly soluble derivative such as, withoutlimitation, a sparingly soluble salt.

Additionally, the compounds may be delivered using a sustained-releasesystem, such as semi-permeable matrices of solid hydrophobic polymerscontaining the therapeutic agent. Various sustained-release materialshave been established and are well known by those skilled in the art.Sustained-release capsules may, depending on their chemical nature,release the compounds for a few weeks up to over 100 days. Depending onthe chemical nature and the biological stability of the particularcompound, additional stabilization strategies may be employed.

Other delivery systems such as liposomes and emulsions can also be used.

E. Dosages

A therapeutically effective amount refers to an amount of compoundeffective to prevent, alleviate or ameliorate the resistance orrefractory phenomenon to anti-cancer agents such as camptothecin orrelated analog, for example, CPT-11. Determination of a therapeuticallyeffective amount is well within the capability of those skilled in theart, especially in light of the disclosure herein.

For any compound used in the methods of the invention, thetherapeutically effective amount can be estimated initially from invitro assays. Then, the dosage can be formulated for use in animalmodels so as to achieve a circulating concentration range that includesthe effective dosage. Such information can then be used to moreaccurately determine dosages useful in patients.

The amount of the composition, e.g., used as a prodrug, that isadministered will depend upon the parent molecule included therein.Generally, the amount of prodrug used in the treatment methods is thatamount which effectively achieves the desired therapeutic result inmammals. Naturally, the dosages of the various prodrug compounds canvary somewhat depending upon the parent compound, rate of in vivohydrolysis, molecular weight of the polymer, etc. In addition, thedosage, of course, can vary depending upon the dosage form and route ofadministration.

In general, however, the polymeric ester derivatives of7-ethyl-10-hyroxycamptothecin described herein can be administered inamounts ranging from about 0.1 to about 30 mg/kg/dose and preferablyabout 0.2 to about 10 mg/kg/dose, yet preferably from about 0.6 to about6 mg/kg/dose for systemic delivery.

The range set forth above is illustrative and those skilled in the artwill determine the optimal dosing of the prodrug selected based onclinical experience and the treatment indication. Moreover, the exactformulation, route of administration and dosage can be selected by theindividual physician in view of the patients condition. Additionally,toxicity and therapeutic efficacy of the compounds described herein canbe determined by standard pharmaceutical procedures in cell cultures orexperimental animals using methods well-known in the art.

In one embodiment, the treatment of the present invention includesadministering the compounds described herein in an amount of from about0.3 to about 6 mg/kg/dose to a mammal having resistant or refractorycancers to such as CPT and CPT-11 therapies.

Alternatively and preferably, the amounts of the compounds administeredcan be based on body surface of human or other mammals. Thus, thetreatment of the present invention includes administering the compoundsdescribed herein in an amount of from about 0.1 to about 45 mg/m² bodysurface/dose. Preferably, the amounts of the compounds described hereinrange from about 0.2 to about 25 mg/m² body surface/dose. Some preferreddoses include one of the following: 1.25, 2.0 2.5, 3.3, 5, 10, and 16.5mg/m²/dose. Preferably, the amounts administered can range from about1.25 to about 16.5 mg/m² body surface/dose. Alternatively, they can befrom about 2.5 to about 13 mg/m² body surface/dose or from about 2 toabout 5 mg/m² body surface/dose.

The treatment protocol can be based on a single dose administered onceevery three weeks or divided into multiple doses which are given as partof a multi-week treatment protocol. Thus, the treatment regimens caninclude one dose every three weeks for each treatment cycle and,alternatively one dose weekly for three weeks followed by one week offfor each cycle.

The precise dose will depend on the stage and severity of the condition,and the individual characteristics of the patient being treated, as willbe appreciated by one of ordinary skill in the art. It is alsocontemplated that the treatment continues until satisfactory results areobserved, which can be as soon as after cycle although from about 3 toabout 6 cycles or more cycles may be required.

In some preferred embodiments, the treatment protocol includesadministering the amount ranging from about 1.25 to about 16.5 mg/m²body surface/dose every three weeks repeating for about 3 cycles ormore. The amount administered per each cycle can range more preferablyfrom about 2.5 to about 16.5 mg/m² body surface/dose. Alternatively, thecompounds described herein can be administered weekly for three weeks,followed by one week without treatment and repeating for about 3 cyclesor more until the desired results are observed.

In one particular embodiment, the polymeric ester derivatives of7-ethyl-10-hyroxycamptothecin can be administered one dose such as 10mg/m² every three weeks in treatment of colon cancer. The dosage oftreatment cycle can be designed as an escalating dose regimen when twoor more treatment cycles are applied. The polymeric drug is preferablyadministered via IV infusion.

In all aspects of the invention where polymeric conjugates areadministered, the dosage amount mentioned is based on the amount of7-ethyl-10-hydroxycamptothecin rather than the amount of polymericconjugate administered. It is contemplated that the treatment will begiven for one or more cycles until the desired clinical result isobtained. The exact amount, frequency and period of administration ofthe compound of the present invention will vary, of course, dependingupon the sex, age and medical condition of the patient as well as theseverity of the disease as determined by the attending clinician.

Still further aspects include combining the therapy described hereinwith other anticancer therapies for synergistic or additive benefit. Inone particular embodiment, the compounds described herein can beadministered in combination with Erbitux® (cetuximab). 400 mg/m²Erbitux® plus the compounds described herein can be administered as aninitial dose followed by 250 mg/m² weekly until disease progresses.Details of Erbitux® dosage information are described in the packageinsert, the contents of which are incorporated herein.

EXAMPLES

The following examples serve to provide further appreciation of theinvention but are not meant in any way to restrict the effective scopeof the invention.

Example 1 Therapeutic Efficacy of four-armPEG-Gly-(7-ethyl-10-hydroxy-camptothecin) in Human Colorectal TumorXenografted Mice Refractory to CPT-11

Therapeutic efficacy of four-armPET-Gly-(7-ethyl-10-hydroxycamptothecin) against a refractory humanHT-29 colorectal tumor grown in nude mice was determined Human HT-29colorectal tumors were established in nude mice by subcutaneousinjection of 1×10⁶ cells/mouse into a right auxiliary flank. When tumorsreached an average volume of 100 mm³, mice were treated with CPT-11 (40mg/kg/dose; q2d×4). Mice were monitored for tumor growth. On day 15,mice with tumors that did not respond to CPT-11 therapy (tumorvolume≧3×initial tumor volume at the start of CPT-11 therapy) wereconsidered CPT-11 refractory. These mice were selected, randomized anddivided into two groups. One group was treated with MTD of CPT-11 (40mg/kg/dose; q2d×5) and the other group was treated with MTD of four-arm^(40K)PEG-Gly-(7-ethyl-10-hydroxycamptothecin) (compound 9) (10mg/kg/dose q2d×5) starting day 16. The drugs were administeredintravenously via the tail vein.

The results are set forth in FIG. 1. Tumors continued to grow in theCPT-11 refractory mice further treated with CPT-11. On day 42, tumorvolume increased by 255% compared to day 15. In the mice treated withfour-arm ^(40K)PEG-Gly-(7-ethyl-10-hydroxy-camptothecin) (compound 9),tumor volume decreased by 25% compared to day 15 on day 42.29% and 100%of animals treated with CPT-11 were sacrificed by day 42 and 54respectively due to excessive tumor burden (>1,650 mm³). In the grouptreated with four-arm ^(40K)PEG-Gly-(7-ethyl-10-hydroxycamptothecin),only 1 of 7 animals was sacrificed on day 63.58% of the mice treatedwith four-arm ^(40K)PEG-Gly-(7-ethyl-10-hydroxycamptothecin) hadtumors<1,650 mm³ by day 72. The results show that four-arm^(40K)PEG-Gly-(7-ethyl-10-hydroxycamptothecin) has therapeutic activityin the treatment of CPT-11 refractory cancer. The data in FIG. 1represent mean±standard deviation (n=7).

Without being bound by any theory, the therapy using the compoundsdescribed herein unexpectedly avoids resistance associated with CPT-11therapy. The therapy described herein provides ways to treat cancersmore effectively by avoiding and reducing potential drug resistance.Patients and clinicians can benefit from unexpected lack of resistanceto the compounds described herein as compared to CPT-11 based therapy intreatment of cancer.

Example 2 Therapeutic Efficacy of four-armPEG-Gly-(7-ethyl-10-hydroxy-camptothecin) in Human Colorectal TumorXenografted Mice Refractory to CPT-11 in the Second Round Treatment

Human HT-29 colorectal tumors were established in nude mice bysubcutaneous injection of 1×10⁶ cells/mouse into a right auxiliaryflank. When tumors reached an average volume of 100 mm³, mice weretreated with CPT-11 (40 mg/kg/dose; q2d×4). Mice were monitored fortumor growth. On day 15, mice that responded to CPT-11 therapy (micethat had tumor volumes<3× initial tumor volume at the start of CPT-11therapy, i.e., mice considered CPT-sensitive) were selected, randomizedand divided into two groups. One group was further treated with MTD ofCPT-11 (40 mg/kg/dose; q2d×5) and the other group was treated with MTDof four-arm ^(40K)PEG-Gly-(7-ethyl-10-hydroxycamptothecin) (10mg/kg/dose q2d×5) starting day 16. The drugs were administeredintravenously via the tail vein.

The results are set forth in FIG. 2. On day 54, in mice treated withCPT-11, tumor volume increased by 1298% compared to day 1. Mice treatedwith four-arm ^(40K)PEG-Gly-(7-ethyl-10-hydroxycamptothecin) had tumorvolume moderately increased by 193%. Additionally, as of day 61, 60%animals were sacrificed in CPT-11 treated group due to excessive tumorburden. No deaths have been recorded in four-arm^(40K)PEG-Gly-(7-ethyl-10-hydroxycamptothecin) (compound 9) treatedgroup on day 61. The results show that four-arm^(40K)PEG-Gly-(7-ethyl-10-hydroxycamptothecin) outperformed therapeuticactivity of CPT-11 and is significantly effective for second round andsubsequent round therapies in the treatment of CPT-11 refractory cancer.The data in FIG. 2 represent mean±standard deviation (n=10).

Example 3 In vitro Cytotoxicity of four-armPEG-Gly-(7-ethyl-10-hydroxy-camptothecin) in the CPT Refractory Cellline

CPT-refractory cell line (CEM/C2) and the corresponding non-refractoryparent cell line (CEM) were treated withPEG-Gly-(7-ethyl-10-hydroxycamptothecin),7-ethyl-10-hydroxycamptothecin, and CPT-11. The CEM/C2 and CEM wereobtained from NCI. The CEM cell lines are acute lymphoblastic leukemiacell lines. The in vitro cytotoxicity of each drug was determined usinga MTS assay. Briefly, cells were placed in 96-well plates (8×10⁴ perwell) and then treated with serial dilutions of four-arm^(40K)PEG-Gly-(7-ethyl-10-hydroxycamptothecin) (compound 9), CPT or free7-ethyl-10-hydroxycamptothecin for 2 days at 37° C. At the end of theincubation, MTS dye was added and incubated for 2 to 3 hours at 37° C.and formation of a colored product (formazan) was measured at 490 nm.The % viability at each drug concentration was calculated as [OD testsamples−background]/[OD controls (no treatment)−background]. Sigmoidaldose response curves were generated by plotting Log(Drug) as a functionof % viability (survival) and IC₅₀ values were calculated using theGraphPad Prism software.

The results are set forth in FIGS. 3 and 4. The cytotoxicity (μM of eachcompound that results in an IC₅₀) shows the in vitro anti-tumor potencyof each compound. This study was used to determine the therapeuticeffect of four-arm PEG-Gly-(7-ethyl-10-hydroxycamptothecin) inCPT-refractory cancer. The four-armPEG-Gly-(7-ethyl-10-hydroxy-camptothecin) was about 10 fold more potentthan CPT-11 in the acute lymphoblastic leukemia cell line refractory toCPT as shown in FIG. 3. In addition, all four-armPEG-Gly-(7-ethyl-10-hydroxycamptothecin), CPT-11 and7-ethyl-10-hydroxycamptothecin showed similar potency in the parent cellline (CEM) as shown in FIG. 4. The results show that four-armPEG-Gly-(7-ethyl-10-hydroxycamptothecin) has potency for treatingcancers resistant to topoisomerase I inhibitors such as CPT.

1. A method of treating a resistant or refractory cancer in a mammal,comprising: administering an effective amount of a compound of formula(I):

wherein R₁, R₂, R₃ and R₄ are independently OH or

wherein L is a bifunctional linker; m is 0 or a positive integer; and nis a positive integer; provided that R₁, R₂, R₃ and R₄ are not all OH;or a pharmaceutically acceptable salt thereof to said mammal.
 2. Themethod of claim 1, wherein the resistant or refractory cancer isselected from the group consisting of solid tumors, lymphomas, lungcancer, small cell lung cancer, acute lymphocytic leukemia (ALL), breastcancer, pancreatic cancer, glioblastoma, ovarian cancer and gastriccancer.
 3. The method of claim 1, wherein the cancer is resistant orrefractory to camptothecin or camptothecin analog therapy.
 4. The methodof claim 1, wherein the cancer is resistant or refractory to CPT-11therapy.
 5. The method of claim 1, wherein the cancer is resistant orrefractory to camptothecin therapy.
 6. The method of claim 1, wherein Lis a residue of an amino acid or amino acid derivative, and the aminoacid derivative is selected from the group consisting of 2-aminoadipicacid, 3-aminoadipic acid, beta-alanine, beta-aminopropionic acid,2-aminobutyric acid, 4-aminobutyric acid, piperidinic acid,6-aminocaproic acid, 2-aminoheptanoic acid, 2-aminoisobutyric acid,3-aminoisobutyric acid, 2-aminopimelic acid, 2,4-aminobutyric acid,desmosine, 2,2-diaminopimelic acid, 2,3-diaminopropionic acid,n-ethylglycine, N-ethylasparagine, 3-hydroxyproline, 4-hydroxyproline,isodemosine, allo-isoleucine, N-methylglycine, sarcosine,N-methyl-isoleucine, 6-N-methyl-lysine, N-methylvaline, norvaline,norleucine, and ornithine.
 7. The method of claim 1, wherein L isselected from the group consisting of —[C(═O)]_(v)(CR₂₂R₂₃)_(t)—,—[C(═O)]_(v)(CR₂₂R₂₃)_(t)—O—, —[C(═O)]_(v)(CR₂₂R₂₃)_(t)—NR₂₆—,—[C(═O)]_(v)O(CR₂₂R₂₃)_(t)—, —[C(═O)]_(v)O(CR₂₂R₂₃)_(t)—O—,—[C(═O)]_(v)O(CR₂₂R₂₃)_(t)—NR₂₆—, —[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)—,—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)O—, —[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)NR₂₆—,—[C(═O)]_(v)(CR₂₂R₂₃O)_(t)—, —[C(═O)]_(v)O(CR₂₂R₂₃O)_(t)—,—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃O)_(t)—,—[C(═O)]_(v)(CR₂₂R₂₃O)_(t)(CR₂₄R₂₅)_(y)—,—[C(═O)]_(v)O(CR₂₂R₂₃O)_(t)(CR₂₄R₂₅)_(y)—,—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃O)_(t)(CR₂₄R₂₅)_(y)—,—[C(═O)]_(v)(CR₂₂R₂₃O)_(t)(CR₂₄R₂₅)_(y)O—,[C(═O)]_(v)(CR₂₂R₂₃)_(t)(CR₂₄R₂₅O)_(y)—,—[C(═O)]_(v)O(CR₂₂R₂₃O)_(t)(CR₂₄R₂₅)_(y)O—,—[C(═O)]_(v)O(CR₂₂R₂₃)_(t)(CR₂₄R₂₅O)_(y)—,—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃O)_(t)(CR₂₄R₂₅)_(y)O—,—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)(CR₂₄R₂₅O)_(y)—,[C(═O)]_(v)(CR₂₂R₂₃)_(t)O—(CR₂₈R₂₉)_(t′)—,—[C(═O)]_(v)(CR₂₂R₂₃)_(t)NR₂₆—(CR₂₈R₂₉)_(t′)—,—[C(═O)]_(v)(CR₂₂R₂₃)_(t)S—(CR₂₈R₂₉)_(t′)—,—[C(═O)]_(v)O(CR₂₂R₂₃)_(t)O—(CR₂₈R₂₉)_(t′)—,—[C(═O)]_(v)O(CR₂₂R₂₃)_(t)NR₂₆—(CR₂₈R₂₉)_(t′)—,—[C(═O)]_(v)O(CR₂₂R₂₃)_(t)S—(CR₂₈R₂₉)_(t′)—,—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)O—(CR₂₈R₂₉)_(t′)—,—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)NR₂₆—(CR₂₈R₂₉)_(t′)—, —[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)S—(CR₂₈R₂₉)_(t′)—,—[C(═O)]_(v)(CR₂₂R₂₃CR₂₈R₂₉O)_(t)NR₂₆—,—[C(═O)]_(v)(CR₂₂R₂₃CR₂₈R₂₉O)_(t)—,—[C(═O)]_(v)O(CR₂₂R₂₃CR₂₈R₂₉O)_(t)NR₂₆—,—[C(═O)]_(v)O(CR₂₂R₂₃CR₂₈R₂₉O)_(t)—,—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃CR₂₈R₂₉O)_(t)NR₂₆—,—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃CR₂₈R₂₉O)_(t)—,—[C(═O)]_(v)(CR₂₂R₂₃CR₂₈R₂₉O)_(t)CR₂₄R₂₅)_(y)—,—[C(═O)]_(v)O(CR₂₂R₂₃CR₂₈R₂₉O)_(t)(CR₂₄R₂₅)_(y)—,—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃CR₂₈R₂₉O)_(t)(CR₂₄R₂₅)_(y)—,—[C(═O)]_(v)(CR₂₂R₂₃CR₂₈R₂₉O)_(t)(CR₂₄R₂₅)_(y)O—,—[C(═O)]_(v)(CR₂₂R₂₃)_(t)(CR₂₄R₂₅CR₂₈R₂₉O)_(y)—,—[C(═O)]_(v)(CR₂₂R₂₃)_(t)(CR₂₄R₂₅CR₂₈R₂₉O)_(y)NR₂₆—,—[C(═O)]_(v)O(CR₂₂R₂₃CR₂₈R₂₉O)_(t)(CR₂₄R₂₅)_(y)O—,—[C(═O)]_(v)O(CR₂₂R₂₃)_(t)(CR₂₄R₂₅CR₂₈R₂₉O)_(y)—,—[C(═O)]_(v)O(CR₂₂R₂₃)_(t)(CR₂₄CR₂₅CR₂₈R₂₉O)_(y)NR₂₆—,—[C(O)]_(v)NR₂₁(CR₂₂R₂₃CR₂₈R₂₉O)_(t)(CR₂₄R₂₅)_(y)O—,—[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)(CR₂₄R₂₅CR₂₈R₂₉O)_(y)—,—[C(O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)(CR₂₄R₂₅CR₂₈R₂₉O)_(y)NR₂₆—,

wherein: R₂₁-R₂₉ are independently selected from the group consisting ofhydrogen, amino, substituted amino, azido, carboxy, cyano, halo,hydroxyl, nitro, silyl ether, sulfonyl, mercapto, C₁₋₆ alkylmercapto,arylmercapto, substituted arylmercapto, substituted C₁₋₆ alkylthio, C₁₋₆alkyls, C₂₋₆ alkenyl, C₂₋₆ alkynyl, C₃₋₁₉ branched alkyl, C₃₋₈cycloalkyl, C₁₋₆ substituted alkyl, C₂₋₆ substituted alkenyl, C₂₋₆substituted alkynyl, C₃₋₈ substituted cycloalkyl, aryl, substitutedaryl, heteroaryl, substituted heteroaryl, C₁₋₆ heteroalkyl, substitutedC₃₋₆ heteroalkyl, C₁₋₆ alkoxy, aryloxy, C₁₋₆ heteroalkoxy,heteroaryloxy, C₂₋₆ alkanoyl, arylcarbonyl, C₂₋₆ alkoxycarbonyl,aryloxycarbonyl, C₂₋₆ alkanoyloxy, arylcarbonyloxy, C₂₋₆ substitutedalkanoyl, substituted arylcarbonyl, C₂₋₆ substituted alkanoyloxy,substituted aryloxycarbonyl, C₂₋₆ substituted alkanoyloxy, substitutedand arylcarbonyloxy; (t), (t′) and (y) are independently selected fromzero or a positive integer; and (v) is 0 or
 1. 8. The method of claim 1,wherein m is from about 1 to about
 10. 9. The method of claim 1, whereinm is about
 1. 10. The method of claim 1, wherein n is from about 28 toabout
 341. 11. The method of claim 1, wherein n is from about 114 toabout
 227. 12. The method of claim 1, wherein n is about
 227. 13. Themethod of claim 1, wherein the compound of formula (I) is part of apharmaceutical composition and the compound of formula (I) includedtherein has about 3.9 units of


14. A method of claim 1, wherein the compound of formula (I) is selectedfrom the group consisting of


15. The method of claim 1, wherein the compound of formula (I) is


16. The method of claim 1, wherein the compound is administered inamounts of from about 0.1 to about 45 mg/m²/dose.
 17. The method ofclaim 1, wherein the compound is administered in amounts of from about1.25 to about 16.5 mg/m²/dose.
 18. The method of claim 1, wherein thecompound is administered in combination with a second chemotherapeuticagent simultaneously or sequentially.
 19. A method of treating aresistant or refractory cancer in a mammal, comprising: administering aneffective amount of a compound of

in amounts from about 1.25 to about 16.5 mg/m²/dose, wherein n is fromabout 28 to about 341 to said mammal.